Aromatic liquid crystalline polyester resins have rigid molecules, which may be present in a liquid crystalline state without entanglement between molecules even in a molten state, and exhibit the behavior of molecular chains being oriented in a flow direction of the aromatic liquid crystalline polyester resin by shear force when being molded.
Due to having these characteristics aromatic liquid crystalline polyester resins have good flowability and resistance to heat, and thus, have been widely used as a material for vehicle parts, electric and electronic parts, and small and precise molded products.
With recent remarkable industrial advances, the uses of aromatic crystalline polyester resins tend to become more sophisticated and specialized. Aromatic liquid crystalline polyester resins have also good fluidity to be available in efficient and economical injection molding. Such aromatic liquid crystalline polyester resins are good, more specifically in heat resistance, resistance to hydrolysis and dimensional stability at high temperature, and mechanical strength, such as bending strength, tensile strength, impact strength, and thus, have extended uses as materials for coil bobbins which need to solder at high temperatures, connectors for electric and electronic parts, various vehicle parts, containers, films, and substrates.
Such aromatic liquid crystalline polyester resins may be prepared by condensation polymerization between at least two different monomers. The condensation polymerization reaction is conducted at a high temperature, thereby producing a gaseous byproduct, which may cause the surface of a reaction product to swell from foaming if not effectively removed. If the surface of the final product swells to an upper top of a reactor, a column for exhausting the gaseous byproduct may be clogged, thus not being able to remove the gaseous byproduct any longer. This may deteriorate physical characteristics of aromatic liquid crystalline polyester prepolymer and aromatic liquid crystalline polyester resins, and further cause a processing hindrance, which requires disassembling and cleaning of the reactor.
Once the gaseous byproduct causes foaming, whether it reaches the upper top of the reactor or not, and is not removed from the reaction product, the resulting synthesized aromatic polyester resin may not have uniform physical properties. As a result, aromatic polyester resin compounds and molded products manufactured from the aromatic polyester resin may have nonuniform, poor physical properties. In particular, the aromatic polyester resin compound may have reduced mechanical strength, and the molded products may undergo blistering when left in high-temperature air or liquid for a long time.